Printed circuit board elements with rigid and flexible printed circuit board portions were proposed with regard to the necessity of foldable and bendable connections for the most varying of applications, starting from applications for the mounting of LEDs in steps, cf. e.g. DE 199 09 399 C1, up to applications of such partially flexible printed circuit boards in electronic devices with a foldable portion, such as mobile telephony devices, yet also portable computers (laptops, notebooks) and so-called handhelds, where, beyond hinge joints, a corresponding flexibility was required with regard to data and signal connections, respectively. Besides the application for foldable and/or bendable connections, rigid-flexible printed circuit board elements can also be used for so-called flex-to-install applications, in which the flexible printed circuit board part is bent only once in order to establish a connection between two printed circuit boards (e.g. motherboard, daughtercard), whereupon the flexible printed circuit board will then remain in this state. The structure of rigid-flexible printed circuit boards and their production, respectively, has been described in various documents, such as in EP 1 659 840 A1, WO 2005/055685 A1 or WO 2004/110114 A1. In these rigid-flexible printed circuit boards, the flexible printed circuit board portions form a type of film hinge between rigid printed circuit boards in order in this manner to enable a pivoting movement between the rigid printed circuit board portions. Copper connections pass over these flexible printed circuit board portions in a conventional manner.
On the other hand, it has already become known to integrate optical signal connections in printed circuit boards, cf. e.g. WO 2005/064381 A1, AT 503 027 B1 or US 2002/0028045 A1. Thus, the functionality of the printed circuit boards is substantially increased, and highly complex product applications can be realized, wherein a further miniaturization of the printed circuit boards, an increase in the integration density of switching characteristics and thus a higher product added value are rendered possible. Such printed circuit boards with optical connections can be used in cases where the applications require the transmission of large amounts of data between components or functional units and/or a space-saving design of the connection paths. So far, however, these integrated optical connections have been practically restricted to rigid printed circuit boards, even though in the aforementioned US 2002/0028045 A1 an embodiment with an optical connection on a flexible substrate has already been described. Intrinsically, however, this document relates to the mounting of optical connections on multi-component modules (MCMs), and not on printed circuit boards, and the flexible printed circuit board is only described there in order to be able to produce a flexible installation and, in doing so, an optical connection to another module, production inaccuracies being compensated by means of the flexibility.
Now the invention is concerned with the object of combining the two aforementioned technologies, namely rigid-flexible-rigid printed circuit board elements on the one hand, and optical connections integrated in printed circuit boards, i.e. optical waveguides, on the other hand, in an efficient manner, in order in this manner to combine the advantages of transmitting high data rates with low space and shielding outlay and of increasing the reliability and design options, and to provide a new high-tech printed circuit board element that offers additional, new options to the electronics sector.